Over 70% of the planet's surface is covered by water. Of all the available water on the planet, only 2.5% is fresh water, the remaining 97.5% is seawater. Of the 2.5% fresh water on the planet, only 0.4% is readily available for human usage with a majority of the earth's fresh water stored as ice at the poles or as inaccessible ground water.
There is a shortage of water suitable for drinking and water suitable for commercial use. In some countries, long-lasting drought and critical water shortages have reduced economic growth and may eventually cause the depopulation of villages, towns, and entire regions. An abundance of fresh water exists in other parts of the world, but in many cases the water is polluted with chemicals from industrial sources and agricultural practices.
Humanity faces major challenges in meeting our future water needs. There are over 300 million people living in regions with severe water shortages. That number may increase to 3 billion by 2025. The United Nations reports that about 9500 children die each day because of low quality drinking water. The increase in the world population has caused a corresponding increase in the demand for portable drinking water, while the amount of water available has not changed. Ongoing, we need to create or find new water resources at a price-point and in a way that supports both economic growth and environmental guardianship.
Over the last half century, there has been a 300 percent increase in water consumption. All of the continents are experiencing falling water tables: this is especially true for the Southern Great Plains of the United States, the Southwest United States, Northern Africa, Southern Europe, the Middle East, Southeastern Asia, and China. Therefore, as fresh water resources are used up and polluted by mankind; we are forced to consider the largest water supply on Earth, the oceans and seas.
Evaporation and reverse osmosis are two typical methods of producing potable water from sea water or salt water. Evaporation methods involve heating the sea water to produce water vapor, condensing the water vapor, and then separating the condensed water from the sea water. Reverse osmosis is a process utilizing a membrane in which solutions are purified using hydraulic pressure. The salt ions or other contaminants are omitted by the reverse osmosis membrane while purified water is pressed through the membrane. Reverse osmosis can remove about 95% to 99% of the dissolved salts, silica, colloids, biological materials, pollution, and other contaminants from the water.
The largest known supply of water are the oceans. The desalination of ocean water by means of a land-based plant presents many problems for an output large enough to satisfy a large population. For example, the purification of oceanwater through evaporation methods consume enormous amounts of energy for land-based plants.
Land-based plants that purify water through reverse osmosis methods create larges amounts of effluent made up of the dissolved solids removed from the sea water. This effluent, or concentrate, has such a high concentration of dissolved solids and salts, that simply dumping the concentrate into the surrounding waters would eventually kill the surrounding marine life and hurt the local ecology, for a land-based plant. Also, the effluent that emerges from land-based reverse osmosis water purification plants has a higher density than sea water, therefore, the concentrate sinks and does not mix efficiently with the sea water when typically dumped into the surrounding water of a land-based plant.
In addition, dumping the effluent into the surrounding water would incrementally increase the salinity of the water taken into the land-based plant and clog the membranes of the reverse osmosis system. When a membrane in a reverse osmosis system is severely clogged it must be removed and treated to remove the clogging material. In some cases, the clogging material cannot be eliminated and the membrane must be discarded and replaced.
Hence, it can be seen that potable water produced from reverse osmosis desalination plants based on land is expensive and creates large engineering problems for disposing of the produced effluent. Therefore, despite the shortage of fresh water, only a small percentage of the world's potable water is produced by reverse osmosis methods. The need exists for a system of consistently and reliably generating potable water using a desalination technology that does not have the engineering and environmental issues that a land-based seawater purification plant presents.
To date, fresh water production from the ocean has focused on the desalination of easily accessible surface seawater through energy intensive coastal facilities. Unfortunately, coastal surface waters suffer from much of the same contamination sources and human interference as do ground water and municipal water supplies. However, there is a source of pure, uncontaminated water which has yet to be tapped, deep ocean water.
Deep ocean water starts its long journey from the polar regions to the tropical zone by moving along the world's “deep water conveyor” through thermohaline circulation. Originating at the poles where fresh water freezes and leaves denser, colder water to sink to the depths of the ocean, this deep water then travels along the ocean bottom towards the tropical regions to replace water being evaporated from the surface at a rate of approximately 1 cm/day.
The oceans are basically separated into three identifiable regions. The surface, or euphotic zone, is generally identified as the top 100 meters and represents the mixed-surface layer where direct interaction with the atmosphere and surface waters can be translated throughout the 100 meter water column. At approximately the 100 meter mark, the thermocline layer begins and extends to approximately the 300-400 meter depth and is subject to fluctuations from tidal influences and internal waves. Below the influences of the thermocline exist the depths of the ocean which are not influenced through any manner by surface phenomena. In Hawaiian waters, the deep ocean water existing below 500 meters originated primarily from around Antarctica and/or from the Arctic and has traversed thousands of miles along the bottom of the Pacific Basin over thousands of years.
Because of the availability of sunlight in the surface layers, a majority of the biological activity of the ocean occurs in the surface or euphotic zone. Photosynthesis and other biological activities in this layer utilize much of the natural nutrient content thereby making deep ocean water nearly 50% more enriched with those nutrients necessary to support natural photosynthetic activity than the surface seawater. This phenomena, coupled with the extreme cold temperatures and pressures experienced at depth, leaves little opportunity to support non-photosynthetic life—including bacteria and viruses. Therefore, void of most life with virtually no interaction or mixing with the upper layers, deep ocean water is nutrient enriched over surface water and effectively void of natural pathogens or chemical contamination from human societies.
Known ship-board water desalination systems are designed and operated for ship-board consumption of water, and thus are designed and operated according to various maritime standards. Maritime standards for water desalination systems and water quality are less stringent than those regulations, standards, and requirements governing the design and operation of land-based desalination plants and systems, especially those promulgated by the United States, the United Nations and the World Health Organization. With the world's increasing shortage of potable water, a need exists to alleviate this shortage. Thus, the need exists for methods and systems that can be utilized at sea to provide desalinated water for land-based consumption of water, which can be produced, stored, maintained and transported consistent with those regulations, standards and requirements governing the design and operation of land-based water desalination plants, systems and water quality standards. Furthermore, all of these known systems harvest water from the immediate vicinity of the ship, and thus the water they extract is from within a few feet of the ocean surface.
What is therefore now needed is a new source of clean, safe, cost-effective potable water. The present disclosure addresses this and other needs.